Flame resistant cellulosic materials



liliiwlifle 18 4 t o rt FLAME RESISTANT CELLULOSIC MATERIALS Wilson A. Reeves, Metairie, Rita M. Perkins, New Orleans,

and George L. Drake, Jr., Metairie, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed July 25, 1963, Ser. No. 297,724

5 Claims. (Cl. 117-622) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of Amer- This invention is a further improvement in or modification of the invention described and claimed in US. Patents No. 2,772,188 and No. 2,983,623. More particularly, this invention relates to the treatment of cellulosic materials with a partially polymerized water soluble product containing a further polymerizable polymer which contains phosphorous and nitrogen, and which is insolubilized within the cellulosic material with ammonia, thereby producing a flame retardant cellulosic material having improved strength retention after chlorine bleaching and scorching, and having little or no yellowing of white cellulosic materials after bleaching with chlorine.

US. Patent No. 2,772,188 defines the nature of the further-polymerizable compounds as methylol-phosphorus polymers in one of the water soluble Stages when applied to the cellulosic materials. The invention then describes a process to further polymerize methylol-phosphorus polymers without the use of heat. This further polymerization is accomplished by using ammonia, in the form of gaseous ammonia, ammonium hydroxide, a solution of ammonia in an inert solvent, or as ammonia released in situ by the reaction of a compound capable of releasing ammonia, e.g., an ammonium salt of a weak acid, such as ammonium acetate.

US. Patent 2,983,623 describes and claims an improved method of insolubilizing the further-polymer-izable methylolphosphorus polymeric materials by treating with gaseous ammonia first and aqueous ammonia afterwards. The process described in this patent is briefly: impregnation of a cellulosic material with an aqueous solution or dispersion of a further-polymerizable methylol-phosphorus polymeric material; drying the cellulosic material; treating the cellulosic material in ammonia gas; treating the cellulosic material in aqueous ammonia; washing, rinsing, and drying the cellulosic material.

Whereas any of the further-polymerizable methylolphosphorus polymeric materials referred to in Patent 2,772,188 are satisfactory for the processes of Patent 2,983,623, a particularly suitable polymeric material is claimed to be the reaction product of tetrakis(hydroxymethyl)phosphonium chloride (THPC) and urea. Scoured and bleached cotton fabric treated by this process was flame resistant, passing the standard vertical flame test (Fed. Spec. CCCT-191b). The treated fabric was fairly stiff, and when given a chlorine bleach turned yellow. Furthermore, after chlorine bleaching and scorching, the fabric retained only 25-30% of its warp breaking strength.

It is the object of this invention to provide a method .of preparation 'of a precondensate and a process for the Patented Oct. 4, 1966 application of the precondensate to impart improved flame resistance to cellulosic materials.

A further object of this invention is to provide white cellulosic materials which will show virtually no discoloration after chlorine bleaching.

Another object of this invention is to provide white cellulosic materials which retain essentially all of their breaking strength after chlorine bleaching and scorching.

Still another object of this invention is to provide a method of producing cellulosic materials which retain their flame-retarding properties after frequent washings.

These and other objects of this invention will be apparent to those skilled in the art of making flame retardant cellulosic materials.

In general, the process of this invention comprises reacting a further polymerizable methylol-phosphorus polymeric material containing a methylol-phosphorus group with ammonia.

Methylol-phosphorus polymeric materials are produced by reacting at least one compound of the group tetrakis (hydroxymethyl)phosphonium chloride, tris(hydroxymethyl)phosphine oxide and phosphorus linked methylol group containing derivatives thereof with compounds containing a plurality of groups which yield condensation products with a phosphorus linked methylol group.

The process of this invention is particularly useful in the insolubilization of nitrogen methylol-phosphorus polymers with ammonia. Preferred nitrogen methylolphosphorus polymers are produced by reacting at least one phosphorus compound of THPC and/ or THPO with a water soluble amide, such as tris(2-carbamoylethyl) amine or ethyl carbamate.

In accordance ,with this invention, any cellulosic material such as cotton, rayon, paper, jute, ramie, and the like may be treated, but the invention is particularly effective when applied to the treatment of cellulosic textiles.

In preparing the further polymerizable nitrogen methylol-phosphorus polymers, the aforementioned compounds are mixed with water and partially polymerized to form a precondensate- This may beat anytemperature from room temperature to the reflux temperature. When the partial polymerization takes place at the reflux temperature, the time may vary up to 3 hours, although one-half hour is usually adequate. Aparticularly suitable polymeric material is the reaction product of tetrakis (hydroxymethyl)phosphonium chloride (THPC) and tris (2-carbamoylethyl)amine (TCEA), in a ratio of 63 parts of THPC with 16 parts of TCEA in 81 parts of water. This precondensate can be stored over a period of several months at or below room temperature.

In preparing the solution to treat the cellulosic materials, the precondensate is diluted with buffered water yielding an aqueous solution containing about 20 to 30% THPC and 5 to 10% TCEA. The pH of the aqueous solution is 3.5 to 6.5.

The cellulosic material is impregnated with the aqueous solution preferably by padding, although other impregnating techniques may be used; the excess solution is removed -by passing the cellulosic material through squeeze rolls, centrifuging, or other methods. The cellulosic material is then dried. The drying temperature can vary from room temperature to 170 C., although -90" C. is preferred; the drying time varies from several hours (atv room temperature) to a few minutes at the higher temperatures. For example, drying of the cellulosic material can be effected in a conventional forced hot air oven for 4 minutes at 80 C.

Insolubilization with ammonia is accomplished in two steps. First the dried cellulosic material containing the further polymerizable methylol-phosphorus polymer is exposed to gaseous ammonia and then to ammonium hydroxide. The gaseous ammonia may be applied at temperatures of from about C. to about 100 C.; the aqueous ammonia may be from about 1 to about 28% ammonium hydroxide. The treated cellulosic materials are then washed and dried.

Cellulosic materials treated in accordance with this invention have improved flame retardant properties which are retained after repeated launderings. When cellulosic materials treated in accordance with this invention are given a chlorine bleach and subsequent-1y scorched, the warp breaking strength retention is more than about 80%. Fabrics so treated have only slightly improved crease resistance.

The following examples illustrate the methods of carrying out the invention but the invention is not restricted to these examples. Treated fabrics were tested by the standard methods of the American Society for Testing Materials, Philadelphia. Breaking strength was determined by the one inch strip method; crease recovery by the Monsanto method; damage by chlorine, by ASA method, No. L14.1261961; and flame resistance by the standard vertical method, Fed. Spec. CCC-T-191b. The percentages are by weight.

EXAMPLE 1 A precondensate was prepared by refluxing for 30 minutes 397 parts of tetrakis(hydroxymethyl)phosphonium chloride, 100 parts of tris(2-carbamoy-lethyl)amine, and 506 parts of water. The solution was cooled rapidly and stored in a refrigerator until used (Solution A).

A buffered water solution was prepared by adding parts of ammonium acetate (NH Ac) to 635 parts of water (Solution B).

A piece of white herringbone twill was impregnated with a solution prepared by mixing 67 parts of Solution A and 33 /2 parts of Solution B, then passed through squeeze rolls to give about a 90% wet pick-up. The impregnated fabric was dried 4 minutes at 85 C. The dry fabric was exposed to gaseous ammonia at room temperature for 2 minutes, and then placed in a 10% ammonium hydroxide solution at room temperature for 2 minutes. The treated fabric was thoroughly washed in water and air dried.

The treated fabric was flame resistant, passing the standard vertical flame .test. The fabric had a warp breaking strength of 86.6 pounds. After a chlorine bleach and scorch, the fabric had a warp breaking strength of 83.1 pounds, and was only slightly yellowed.

EXAMPLE 2 A sample of OD sateen was treated in the same manner described in Example 1. The treated fabric had a weight increase of 7.5% and a char length of 4.3 inches. After a 3 hour boil in an aqueous solution containing 0.2% anhydrous sodium carbonate and 0.5% soap, the treated fabric Was still flame resistant, passing the vertical flame test with a 3.9 inch char length. The fabric had a wrinkle recovery angle of 200 as measured on the Monsanto crease tester.

EXAMPLE 3 Three pieces of OD sateen were impregnated with a solution prepared by mixing 100 parts of Solution A and 67 parts of Solution B, then passed through squeeze rolls to give about a 70% wet pick-up. The impregnated fabrics were dried 4 minutes at 80 C. The dry fabric was exposed to gaseous ammonia at room temperature and then placed in a 10% ammonium hydroxide solution. The treated samples were water washed and air dried. Data appears in Table I.

T able I Exposure Time (Min) Char Add-0n, 1, Length, Percent Percent Inches NH; 10% NII 0H EXAMPLE 4 A small pilot plant application was made on OD sateen. The treating solution was prepared in a manner similar to Example 3. Thirteen yards of fabric cut to a ten-inch width, was impregnated with the treating solution, and the excess solution was eliminated by passing the fabric through squeeze rolls. The impregnated fabric was then dried and chemically fixed in one continuous operation. Drying was done in 4% minutes at 80 C. in an elec trically heated oven. After drying, the fabric was exposed in an enclosed tank containing gaseous ammonia at about 27 C. for 2 minutes, 3 seconds. The fabric next passed through a tank of 10% NH OH (2 minutes exposure time) and then was washed with water.

Physical properties of the treated fabric are shown in Table II.

EXAMPLE 5 OD sateen was treated in a manner similar to Example 3, except that the NH gas was at C. and the exposure times were as shown in Table III. Percent phosphorus in the treated fabrics are also shown in Table III.

T able III Reaction time (min) P Perc ent NH. 10% NH OH 2 1. 68 l 2 l. 60 2 2 l. 60

EXAMPLE 6 A precondensate was prepared by mixing 397 parts of THPC, 100 parts of TCEA and 506 parts of water; buffering to a pH 4.7 with NH Ac; refluxing for 30 minutes; and cooling rapidly.

The treating solution was prepared by using 100 parts of the precondensate and 67 parts of Solution B (Example 1). A sample of OD sateen was treated using this solution in a manner similar to Example 1, except that the fabric remained 5 minutes in the ammonium hydroxide. The treated fabric was flame resistant, passing the standard vertical flame test.

EXAMPLE 7 A precondensate was prepared by mixing 397 parts of THPC, 100 parts of TCEA and 506 parts of water; refluxing for 3 hours; and cooling rapidly.

The treating solution was prepared by using 100 parts of this precondensate and 67 parts of Solution, B (Example 1). A sample of OD sateen was treated using this solution in a manner similar to Example 1, except that the fabric remained in the ammonium hydroxide 5 minutes. The treated fabric passed the standard vertical flame test with a char length of 4.05 inches.

EXAMPLE 8 A precondensate was made by mixing 397 parts of THPC, and 148 parts of ethyl carbamate, and 455 parts of water; buffering to pH 3.5-4 with NH Ac; refluxing 30 minutes; and cooling rapidly (Solution 3).

Samples of 0D sateen were treated in a manner described in Example 1. Variations in solution concentra- 6 EXAMPLE 11 A solution was prepared following the procedure recommended in U.S. Patent No. 2,983,623 using 63 parts of THPC, 16 parts urea, and 81 parts water. This solution was buffered to pH 3.5 to 4.0 with ammonium acetate, refluxed 30 minutes, and cooled rapidly. To 100 parts of this solution, 6 7 parts of Solution B (Example 1) was added. The pH of this mixture of solutions was 4.6.

A sample of herringbone twill was treated in the manner described in Example 1. The treated fabric had a weight increase of 13.7%, a phosphorus content of 2.01% and a char length of 3 .25 inches.

The breaking strength (warp) of the treated cotton tions, drying conditions, and chemical fixation are shown fabric was 91.6 pounds. The fabric was submitted to in Table IV. chlorine bleach and scorching, and tested again. The

T able IV Treating Bath, Drying Conditions Reaction Time Parts of (Min) Char Length, P,

Inches Percent Soln- Solu- Time Temp, NH; 10% tion #3 tion B (min) C. NH OH EXAMPLE 9 breaking strength (warp) was then 22.9 pounds, and the A precondensate was made by mixing 39 7 parts of THPC, 100 parts of ethyl carbamate and 506 parts of water; buffering to pH 3.5-4 with NH Ac; refluxing minutes; and cooling rapidly (Solution 4).

Samples of OD sateen were treated in a manner defabric had yellowed.

We claim:

1. A process for treating a cellulosic material which comprises:

(a) treating said cellulosic material with an aqueous scribed in Example 1. Variations in solution concentra- 40 Solution of a -p y methylol P tions, drying conditions, and chemical fixation are shown P1101118 Polymeric material containing at least 0116 i T bl V free methylol group attached to a phosphorus atom Table V Treating Bath, Drying Conditions Reaction Time '1. Parts of (Min) Char i Length, P,

Inches Percent Soln- Solu- Time Temp, NH; 10% tior1#4 tionB (min) 0. NILOH 1 100 67 4 so 1 1% 3.9 100 67 4 so 1 1 4.2 1.8 100 67 4 so 2 2 4.0 1.7 134 67 4 so 1 1 4.6 1.6 134 61 4 s0 2 2 4.2 1.6

EXAMPLE 10 prepared by treating a precondensate consisting of a partially polymerized mixture of a phosphorus-con- A Sample Whltfi hfi'fflflgbcjfne l Was treated 115mg tainin'g compound selected from the group consistthe same precondensate described in Example 8. The ing f tetpakis(hydroxymethyl) phosphonium hl ratio of the precondensate to the buffered water solution id d tris(hydroxymethyq1)phosphjne id d a was 3 to 2. The fabric was padded to a Wet pick-up 0f 5 water-soluble amide selected from the group consist- 95%, and dr1ed for 4 minutes at 85 C. ma forced-draft ing of tris(2-carbamoylethy.l)amine and ethyl carelectric oven. The treated fabric was then exposed at bamate, said aqueous solution containing from about room temperature to ammon a gas for two minutes, and 20 to 30% of the phosphorus-containing compound to 10% ammonium hydroxide for 2 mlnutes. After and from about 5 to 10% of the water-soluble amide washing with hot running tap water, the treated fabric and being buffered to a pH of from about 3.5 to was air dried. The weight increase of the fabric was about 6.5 with aqueous ammonium acetate; 10.2%. (b) drying the thus-treated cellulosic material at a The treated fabrlc had a warp breaking strength of temperature of from about room temperature to about 83.2 pounds. After a chlorine bleach and scorch treat- 170 (3., for a period of time from about 1 minute ment, the fabric was only slightly yellowed, and had a to about 4.75 minutes, the longer period of time warp breaking strength retention of 84%.

being applicable to the lower temperature;

4. The process of claim 1 wherein the water-soluble amide is tris(2-carbam oylethy1) amine.

5. The process of claim 1 wherein the water-soluble amide is ethyl earbarnate.

References Cited by the Examiner UNITED STATES PATENTS 2,772,182 11/1956 Reeves et al. 117-136 10 2,983,623 5/1961 Coatcs l1762.2

WILLIAM D. MARTIN, Primary Examiner.

T. G. DAVIS, Assistant Examiner. 

1. A PROCESS FOR TREATING A CELLULOSIC MATERIAL WHICH COMPRISS: (A) TREATING SAID CELLULOSIC MATERIAL WITH AN AQUEOUS SOLUTION OF A FURTHER-POLYMERIZABLE METHYLOL PHOSPHORUS POLYMERIC MATERIAL CONTAINING AT LEAST ONE FREE METHYLOL GROUP ATTACHED TO A PHOSPHORUS ATOM PREPARED BY TREATING A PRECONDENSATE CONSISTING OF A PARTIALLY POLYMERIZING MIXTURE OF A PHOSPHORUS-CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF TETRAKIS(HYDROXYMETHYL) PHOSPHONIUM CHLORIDE AND TRIS(HYDROXYMETHYL) PHOSPHINE OXIDE AND A WATER-SOLUBLE AMIDE SELECTED FROM THE GROUP CONSISTING OF TRIS(2-CARBAMOYLETHYL) AMINE AND ETHYL CARBAMATE, SAID AQUEOUS SOLUTION CONTAINING FROM ABOUT 20 TO 30% OF THE PHOSPHORUS-CONTAINING COMPOUND AND FROM ABOUT 5 TO 10% OF THE WATER-SOLUBLE AMIDE AAND BEING BUFFERED TO A PH OF FROM ABOUT 3.5 TO ABOUT 6.5 WITH AQUEOUS AMMONIUM ACETATE; (B) DRYING THE THUS-TREATED CELLULOSIC MATERIAL AT A TEMPERATURE OF FROM ABOUT ROOM TEMPERATURE TO ABOUT 170*C., FOR A PERIOD OF TIME FROM ABOUT 1 MINUTE TO ABOUT 4.75 MINUTES, THE LONGER PERIOD OF TIME BEING APPLICABLE TO THE LOWER TEMPERATURE; (C) EXPOSING THE DRIED, TREATED CELLULOSIC MATERIAL TO GASEOUS AMMONIA FOR A PERIOD OF TIME FROM ABOUT 1/2 MINUTE TO ABOUT 2 MINUTES, FROM ABOUT 25*C. TO ABOUT 100*C.; (D) IMMERSING THE AMMONIA GAS-TREATED CELLULOSIC MATERIAL IN A 1%-28% AQUEOUS AMMONIA SOLUTION FOR A PERIOD OF TIME FROM ABOUT 1/2 MINUTE TO ABOUT 5 MINUTES, AT ROOM TEMPERATURE; THEN (E) WASHING, AND DRYING THE RESULTING CELLULOSIC MATERIAL. 